Fiber optic cables generally include a fiber optic strand and one or more outer jackets. When the cable experiences temperature changes, one or more of the jackets can contract or expend at a different rate from the inner cable members, including the fiber strand. There is a need for devices and methods that reduce the effects of differential thermal expansion and contraction characteristics of the fiber optic cable.
In telecommunications networks installed in the field, it is known to have a large multi-fiber cable, such as an outside plant (OSP) cable, including multiple sub-units or cables within an outer jacket, with a strength member extending along with the sub-units. Each of these sub-units may include one or more optical fiber strands within an outer jacket. As the larger cable is extended throughout the area to which service is desired, at a plurality of fiber access enclosures, fiber strands in one or more of the sub-units with the larger cable may be extracted and spliced, or otherwise connected to a customer drop cable. The remaining sub-units within the larger cable continue on the route of the larger cable to be split off at a further fiber access enclosure. Those sub-units, which are passed through an enclosure with connecting to customer or other cables, are referred to as “expressed” sub-units.
Fiber access enclosures are often surface or pedestal mounted enclosures, subject to extremes of temperature due to the external environmental conditions. The materials in the sub-units, such as the fiber strands, the external jackets and potentially water blocking gel within the jacket about the fiber strands, may all react differently to exposure to these temperature extremes. For example, the jackets may contract more in cold temperatures than the relatively stable fiber strands. Differential contraction of the jacket with respect to the fiber strands can cause micro-bending of the fiber strands with the sub-units, leading to unacceptable attenuation losses with the fiber strands.
It is desirable to provide for the differential thermal expansion and contraction characteristics of the elements of the sub-units to be accommodated to reduce the level of attenuation induced by temperature extremes.